In Huston et al. U.S. Pat. No. 6,087,666 entitled Optically Stimulated Luminescent Fiber Optic Radiation Dosimeter, an optically-stimulated luminescent radiation dosimeter system is disclosed. This system includes a radiation-sensitive optically-stimulated dosimeter which utilizes a doped glass material, disclosed in Huston et al. U.S. Pat. No. 5,811,822 entitled Optically Transparent, Optically Stimulable Glass Composites for Radiation Dosimetry, disposed at a remote location for storing energy from ionizing radiation when exposed thereto. The doped glass material releases the stored energy in the form of optically-stimulated luminescent light at a first wavelength when stimulated by exposure to light energy at a stimulating second wavelength. A fiber-optic waveguide communicates the released light to a photo detector at a remote location. Radiation dosage is measured in real-time at the remote location.
Radiotherapy approaches for treating humans and animals are known. Simply stated, oncologists irradiate tumors or “targets” to retard or eliminate the cancer. A brief review of the state-of-the-art treatment is warranted.
An oncologist in planning treatment physically examines a patient, looks at the patient's pathology, and observes previously generated patient images. Using all this information, the oncologist generates a treatment plan. This plan includes irradiating the tumor (hereafter target) at multistage intervals (for example, 36 discrete treatments or fractions) along a group of paths with the target at the point of path intersection. Since the radiation passes through healthy tissue on its way to and from diseased tissue, multiple paths for the administration of radiation are chosen. In that way, damage to healthy tissue is minimized and irradiation of the target maximized because of its location at the intersection of the group of paths.
Due to the nature of most cancers, it is required that the target receives the maximum prescribed dose of the oncologist's plan. Untreated tumor leads directly to recurrence of the cancer being treated. For this reason, typical treatment planning includes irradiating a volumetric “margin” around the target. Dependent upon target location, this volumetric margin can vary considerably. Some margin is needed due to uncertainty in knowing the precise boundary of the tumor. However, extra margin is applied due to patient and tissue/organ motion. Eliminating this extra margin can reduce the normal tissue toxicity and also allow for a higher dose to be administered to the tumor.
In the treatment planning process, the patient is placed in a treatment position and CT, MRI, PET and other images and scans are generated. The scans are fused to produce a three-dimensional digitized image of the patient in the treatment position. The target is identified in the three-dimensional digitized image of the patient. Thereafter, radiation treatment is delivered to the target through the patient in accordance with the oncologist's plan.
The oncologist typically predicts the total dosage delivered to the target utilizing known software in conjunction with his or her generated treatment plan. Dosage delivered at each discrete treatment can be the subject of a predicted irradiation pattern, usually at the target within the patient. In fact, the predicted irradiation pattern can be determined for any points within the three-dimensional digitized image obtained for the treatment plan.
For a recent disclosure illustrating the planning process, please see Pugachev et al. U.S. Pat. No. 6,504,899 issued Jan. 7, 2003.
This idealized description is not to be confused with reality. In general, when radiation therapy treatments are administered, the patient is immobilized and oriented to the treatment machine, lined up with external markers, and irradiated. Despite patient immobilization, internal organ motion can occur between treatments (so-called “inter-fraction” motion) and motion may occur during the treatment (so-called “intra-fraction” motion). To compensate for these motions and to assure that the target receives the prescribed radiation, the volumetric margin around the target is increased. Healthy tissue is irradiated along with the diseased tissue. Further, total dosage intensity at the target is decreased because of limitations of tolerance of the normal tissue which depends on both the dose of radiation and the volume of normal tissue irradiated.
Take for example where the target is in the lung. During breathing, portions of the lung move as much as 3 cm. Compounding the normal movement with patient anxiety during a radiation treatment, irradiating a target in the lung is a dynamic proposition. In the past, for full target irradiation, the margin of the radiation field has been increased considerably with resultant damage to healthy tissue. Similarly, extra rectal tissue is treated to account for prostate gland motion.